At first I tried jailbreaking it with redsn0w, but when redsn0w finishes and says "Done, please continue from iphone" all my iphone shows is a black screen. If I restart the iphone, it just brings me into the same non-jailbroken 4.2.1 that was there before. I also tried it with whited00rs 6 because I realized I wouldn't be able to install any iphone iOS 5 apps jailbroken or not, but no luck with that either. I followed the instructions for whited00rs but it either gives me error 1604 or 1603. I am using the latest version of Itunes if that matters.

At first I tried jailbreaking it with redsn0w, but when redsn0w finishes and says "Done, please continue from iphone" all my iphone shows is a black screen. If I restart the iphone, it just brings me into the same non-jailbroken 4.2.1 that was there before. I also tried it with whited00rs 6 because I realized I wouldn't be able to install any iphone iOS 5 apps jailbroken or not, but no luck with that either. I followed the instructions for whited00rs but it either gives me error 1604 or 1603. I am using the latest version of Itunes if that matters.

Okay, let's try a DFU restore to a stock 4.2.1 IPSW, then attempt the redsn0w jailbreak again... if redsn0w fails on the device again, try the whole process on a different computer with a different USB cable (if available. If not, try a different USB port and cable on the same computer after rebooting it, preferably a USB port straight on the main logic board--the back of a desktop or the sides of a laptop are a good place to look).